This project represents a long-term effort to characterize and quantify auditory processing skills in preschool and school-aged children. Recent results suggest that many of the reported differences between adult and child auditory processing can be traced to the influence of central, attentional factors. The aims of the proposed experiments are to understand and characterize in detail the influence of these central factors on a child s performance in a variety of auditory tasks. The tasks measure how children separate relevant from irrelevant information, or auditory foreground from auditory background . Of special interest is the impact of stimulus uncertainty, such as would occur in real-world listening situations. Preliminary results suggest that children are much more sensitive to uncertainty than are adults. One set of experiments will use the powerful sample-discrimination paradigm in which a child s responses in a tone pattern discrimination paradigm are analyzed to produce detailed information on how the various components in a pattern are weighted and combined. A second set of experiments will measure how children use spatial cues to separate foreground from background , as required in everyday listening to separate relevant speech from irrelevant competition in a reverberant listening environment such as a classroom. A third set of experiments will address basic questions about how children process auditory spatial information. The focus in these experiments will be on children s use of the spectral cues provided by pinna diffraction, and how children might learn to use these cues while the pinnae are growing. Well established virtual auditory space techniques will be used to synthesize and control the stimuli in these experiments. The distinguishing features of the overall study design are that each child is tested repeatedly in all conditions of an experiment, and that in general the testing procedures are adaptations of the rigorous paradigms routinely used to assess adult auditory function. All of the experiments will initially involve children from four to ten years of age who are developing typically, and whose hearing is judged to be normal on the basis of standard audiometric assessment.